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acid chlorides, using the Friedel-Crafts' reaction (see Prep. 100,
p. 210), also of aliphatic ketones and tertiary alcohols with zinc
methyl and ethyl, &c. (Butlerow) or magnesium alkyl halicle

(i)    CH,.COC1  +  Zn(CH3)o =  CH3.C~-C1


OZnCH,                                            xCl

CH, + Zn<


•OZnCI-Ij          /CH3

(CH3),, = CH3.C^-—'


CIL.C^Cl         °+ HoO = CH,.CO.CH, + Zn<        + CH4-

XCH;!                "               ^ Acetone.   '           XOH

:nCH3        /

(2)    CIL.COC1 + 2Zn(CHA, = CH,.Cc-CH.,        + Zn<

\CH;        xci

= CH3.C(OH)(CH3)a
^CHo                         Tertiary butyl alcohol.
An additive compound with zinc methyl is formed, in the
first reaction with one molecule, in the second with two mole-
cules, and the product in each case is then decomposed with
water. The reaction with magnesium methyl iodide is
Acetic Anhydride.—The anhydrides may be regarded as
oxides of the acid radicals, just as ethers are the oxides of the
alcohol radicals, and, like the ethers, both simple and mixed
anhydrides may be prepared. The latter, however, on distilla-
tion decompose, giving a mixture of the simple anhydrides.
C2H,0\0 _ C,H,0\0     C3II80\0
2C5H90/U ~ C,M80/U + C5H90/a
Anhydrides may also be prepared by the action of POC13 on
the potassium salt of the acid in presence of excess of the
latter, the reaction occurring in two phases:
2cri:..cooK + POCL.    =2Ci-i:l.coci + KPO:! +KCI.
CI-L.COOK + CJLOC1 = (CoH,O),O + KC1. '
In addition to the reactions described under the Preparation,
the anhydrides undergo the following changes :
i. With HC1, HBr, and HI they give, on heating, the acid
chloride and free acid,
(CH3CO)2O + HC1 = CH8COC1